Serial ports

[Steve lewis]

Using XP Home I use a serial connection to conect to
industrial equipment and this connection is unreliable.
win 95,98,millenium works ok on the same computer but XP
is unreliable, any ideas ?

 

[w_tom]

More likely a function of how application (program) software
was written. One reason for so much instability in DOS and
Win9x based OSes was that programs accessed hardware
directly. Win NT based OSes channel all hardware access via
OS control. If your application software was doing very
unstandard port access, then all NT based OSes will create
problems.

But to better answer your question, best to start by
describing the application details of serial port you are
using. The only really acceptable use of a serial port is
terminal equipment (ie computer) connected to communication
equipment (ie. modem). Most other implementations are
perversions of the RS-232 standard.

And so we start with which serial port wires are being
used. Besides transmit, receive and signal ground, is your
port using DTR, DSR, etc? IOW which pins interconnect
computer to industrial controller and which are jumpered back
to computer or industrial equipment serial port? Using flow
control - and is it hardware or software flow control?

Welcome to the non-standard Standard called RS-232.

 

[Si Ballenger]

I've got a com port program that is compiled in quickbasic that
runs on win95 thru 2K, but not on an XP machine. Yet the below
used in a batch file seems to access the port OK.

MODE COM1:2400,N,8,1 >nul
ECHO aaaaaaaaaaaa > COM1

 

[Peter Hutchison]

I've got a com port program that is compiled in quickbasic that
runs on win95 thru 2K, but not on an XP machine. Yet the below
used in a batch file seems to access the port OK.

MODE COM1:2400,N,8,1 >nul
ECHO aaaaaaaaaaaa > COM1

XP will not allow direct access to hardware, you must use the
functions in the OS. So your Quickbasic program is too old.
Upgrade to Visual Basic.

Peter Hutchison
Windows FAQ
http://www.pcguru.plus.com/